This invention relates to a fastener installation tool and more particularly to a fastener installation tool having an offset nose assembly with an improved deflector and guard assemblies.
Fastener installation tools having offset nose assemblies are used to provide access to multi-pieced fasteners located between closely spaced workpieces or within small clearance spaces. Installation tools and related nose assemblies are utilized in conjunction with a hydraulic pressure source for installing multi-pieced fasteners by applying a relative axial pulling force, for example, between a pin or mandrel and a collar or sleeve. A lockbolt or swage type fastener is an example of a multi-piece fastener that has a pin and collar adapted to be set with the relative axial pulling force of an installation tool. A blind type fastener is another example of a multi-piece fastener that has a pin and a sleeve adapted to be set with the relative axial pulling force of an installation tool. With both the lockbolt and blind type fasteners, the pin has an elongated shank provided with a pintail or pull portion having a plurality of pull grooves adapted to be gripped by a plurality of chuck jaws in the nose assembly. In the deactuated condition, the chuck jaws will be normally held open to facilitate insertion of the pintail portion into the aperture defined by the opened chuck jaws as well as ejection after the fastener has been set. During actuation of the tool with the pintail portion located in the nose assembly, the chuck jaws will be moved to a closed condition for engagement with the pull grooves whereby the pull grooves will be gripped by the chuck jaws.
A swage anvil is adapted to engage the collar or sleeve, depending upon the type of fastener, and, upon actuation of the tool and with the chuck jaws gripping the pintail portion of the pin shank, as noted, a relative axial pulling force is then applied between the collar or sleeve and pin of the fastener by way of the relative axial force between the chuck jaws and the swage anvil. Typically, the pin or mandrel is provided with a weakened portion or breakneck groove which is located on the pin shank between the pull or pintail portion and the remainder of the shank and is adapted to fracture at a preselected axial load, i.e. pin break load, after the fastener has been set. This results in an installed fastener having a generally flush structure with minimal or no pintail protrusion. In certain tools, the severed pintail portion is ejected rearwardly out through the back end of the tool. The offset nose assembly of the present invention is a tool that has severed pintails ejected from the rear of the offset nose assembly.
The magnitude of the pin break load required to fracture the breakneck groove, however, can result in the generation of a reaction load of significant magnitude. The magnitude of pin break load can be especially high with swage type fasteners since the breakneck groove must be of sufficient strength to withstand the high installation loads required for the swage anvil to swage the collar onto the pin. As a result, in hand held installation tools employing a construction for pass through or rearward ejection, the severed pintail portion could be ejected with a considerable force in the direction of the operator. As a result, it has been a common practice with such tools to utilize a pintail deflector made of an elastomeric material to absorb some of the force of the pintail portion and to deflect the pintail portion away from the operator.
An offset nose assembly may include, for example, a collet and a swage anvil for swaging a collar into the grooves of a fastener pin. In such designs, the swage cavity and first bore of the collet that is adapted to receive passage of severed pintails are radially offset from the axis of the piston which drives a drawbar against the collet. This arrangement allows the radially offset swage cavity to access the fastener pin and collar without interference from the other portions of the offset nose assembly and the fastener installation tool.
It is desirable for an offset nose assembly to be rotatable about the drawbar axis of the offset nose assembly. Such rotatability provides the offset nose assembly with greater access to fastener pins and collars located between closely spaced workpieces or within small clearance spaces. With rotatable offset nose assemblies, cam-out of the drawbar from the piston must be eliminated to avoid harm to the operator of the tool. In the prior art, a roll pin assembly was used to eliminate cam-out of the drawbar in a rotatable offset nose assembly. A roll pin passed through holes machined through the drawbar and collet that locked the drawbar and collet together. This locked construction eliminated cam-out of the drawbar in the prior art rotatable nose assembly. The roll pin would reciprocate back and forth in a slot machined in the swage anvil during use of the offset nose assembly. An example of this prior art assembly is shown in FIG. 5 of U.S. Pat. No. 4,796,455 to Rosier.
The present invention departs from the design of U.S. Pat. No. 4,796,455 by completely eliminating the roll pin approach. In the present invention, the drawbar of the offset nose assembly and the piston of the fastener installation tool are provided with chamfers that are complementary angles of one another that are positively engaged when the drawbar is threaded into the piston of the installation tool. The positive engagement between the drawbar and the piston eliminates cam-out of the drawbar from the piston. Such a design in an offset nose assembly eliminates the need of using the roll pin approach of U.S. Pat. No. 4,796,455. As can be appreciated, the present invention has efficiencies in the manufacture of the offset nose assembly with comparison to U.S. Pat. No. 4,796,455. In the present invention, the use of a roll pin is eliminated, holes do not need to be machined through the drawbar and collet to receive the roll pin and a slot does not need to be machined through the swage anvil. The design of the present invention has efficiencies in its manufacture over the prior art.
It is desirable to equip an offset nose assembly with a pintail deflector that deflects pintails that are severed from fastener pins during the process of swaging a collar into the grooves of a fastener pin. In the prior art, deflectors were often secured to the rear portion of the first bore of the collet with a retaining nut or screw that projected outwardly from the rear portion of the first bore. Additionally, the deflectors were relatively lengthy pieces of elastomeric material that also reduced the effective diameter of the passageway that ejected the severed pintail. With actuation of the tool, the collet would be driven rearwardly causing the retaining nut or screw and deflector to back into a workpiece. Backing into workpieces has the potential of causing damage to soft workpieces made of fragile composite materials. Damage to workpieces must always be minimized. An example of a prior art deflector can be seen in FIG. 1 of U.S. Pat. No. 4,615,206 to Rosier with reference to element 176. Furthermore, the reduction in size of the passageway for ejection of the pintail can lead to pintails being jammed within the passageway which must be removed from the tool in a time consuming process.
The present invention departs from the use of a projecting retaining nut or other such projecting affixation devices for securing relatively lengthy deflectors to the rear portion of the first bore of the collet. An acorn shaped deflector or frusto-conical shaped deflector that has a plurality of tapering beams adapted to deflect a severed pintail from a fastener is used. The deflector is made from a suitable elastomeric material and is thermally adhered or glued to a threaded nut which is threadedly engaged with the rear portion of the collet. The deflector is collapsible and the threaded nut is seated flush with the rear portion of the first bore of the collet. With actuation of the tool, the collet would be driven rearwardly causing the deflector to back into a workpiece which would collapse the deflector and the threaded nut would not engage the workpiece because it is seated flush. No damage can occur to the workpiece with the deflector of the present invention. Additionally, the manner in which the deflector is secured to the collet does not reduce the diameter of the passageway that ejects pintails so the risk of pintails lodging in the passageway is minimized as well.
It is desirable to equip an offset nose assembly with guard assemblies to minimize the pinch points in the offset nose assembly to avoid personal injury to the operator. Prior art guard assemblies are typically attached to the offset nose assembly with screws. Attaching the guard assemblies with screws is a time consuming process and the guard assemblies are easily removed to circumvent the safety features of the offset nose assembly. An example of a prior art deflector can be seen in FIG. 5 of U.S. Pat. No. 4,615,206 to Rosier with reference to element 175.
The present invention departs from the use of guard assemblies that are secured to the nose assembly with a screw. The guard assemblies of the present invention are provided with projections that are adapted to be received in dimples of the swage anvil and the collet. The guard assemblies are not easily removed from the offset nose assembly and are completely contained within the nose assembly envelope which adds to the safety of the present invention.
It is an object of the invention to minimize cam-out of a drawbar of an offset nose assembly from a piston of a fastener installation tool.
It is another object of the invention to provide a compact, fully collapsible deflector that minimizes damage to workpieces during operation of a fastener installation tool.
It is an additional object of the invention to provide guard assemblies that may be snapped onto an offset nose assembly to eliminate all pinch points on the nose assembly.
One object of the invention is achieved by providing an offset nose assembly that generally consists of a drawbar, a swage anvil and a collet. The drawbar has a first diameter portion, a second diameter portion, a third diameter portion and threads disposed at the rearward end of the drawbar. The first diameter portion has an enlarged bearing head and a diameter greater than the second diameter portion. The second diameter portion has a diameter greater than the third diameter portion and transitions from the first diameter portion by a shoulder. The third diameter portion transitions from the second diameter portion by a chamfer. The chamfer is of a preselected angle that is adapted to positively engage a chamfer of a preselected angle of a piston of a fastener installation tool. The swage anvil has a swage cavity and has a first aperture adapted to receive a portion of the first diameter portion of the drawbar. The collet has a first bore and a second bore. The first bore is adapted to receive a chuck jaw assembly for grippingly engaging fasteners. The second bore is adapted to receive the second diameter portion of the drawbar. The collet is slidably disposed within the swage anvil. In the offset nose assembly, the drawbar has a portion of the first diameter portion slidably disposed within the first aperture, the second diameter portion of the drawbar is slidably disposed within the second bore of the collet and the third diameter portion of the drawbar passes through the second aperture of the swage anvil.
Another object of the invention is achieved by providing an offset nose assembly with a deflector. The deflector is attached to a nut that is threadedly engaged with the rearward end of the first bore of the collet. The deflector has a section of a uniform constant outside diameter that integrally transitions to a section that has an outside diameter that gradually lessens along its length. The portion of gradually lessened outside diameter has a plurality of rearwardly extending tapering beams that are collapsible.
An additional object of the invention is achieved by providing the collet of an offset nose assembly with a generally L-shaped guard assembly. The guard assembly is adapted to cover a gap defined between the collet and the swage anvil. The collet has dimples on either side of the exterior surface of the collet and the guard assembly has opposing projections that are disposed in the dimples.